Sunday, May 06, 2007

The Return of The (E)F5

In the early evening of May 3, 1999, a giant tornado plowed through southern suburbs of Oklahoma City, ripping numerous well-constructed homes from their foundations and reducing them to matchsticks and rubble scattered across the landscape. National Weather Service damage surveyors determined that this destruction indicated that the tornado was an F5, the highest rating possible on the Fujita Scale of Tornado Intensity.

Since that time, dozens of destructive tornadoes have roared across the United States, destroying human lives and causing hundreds of millions of dollars in damages. Among them was the Stoughton tornado of August 2005, which flattened homes just two blocks north of mine. However, none of these tornadoes produced the level of complete destruction to be assigned the highest rating. Other tornadoes ballooned to gargantuan proportions in open fields and plains, displaying violent motion to the observers indicative of extreme winds within. Perhaps if one of these tornadoes had contacted a well-constructed, anchored frame house it would have been capable of "lifting it off its foundation and carrying it a considerable distance to disintigrate", the definitive indicator of F5 damage.

On February 1, 2007, the Fujita scale was retired in favor of the Enhanced Fujita Scale, which changes the estimated windspeeds associated with each category to (probably) better reflect the actual windspeeds in tornadoes, and most importantly provides much more detailed "damage indicators" for assessing damage caused by tornadoes that contact and damage many different types of structures, vehicles, trees, etc.

The 2007 tornado season got off to a fast start, producing many destructive and deadly tornadoes, but as with the past seven years, none was quite powerful enough, quite totally and utterly devastating enough for the survey teams to assign the maximum rating.

Until May 4.

As darkness fell that evening, a rotating supercell thunderstorm rapidly intensified as it moved into southwestern Kansas. Not too unusual for spring in the Plains. But then, a huge "wedge" tornado, wider than it was tall, touched down as the storm entered Kiowa County, taking dead aim on the unfortunate small town of Greensburg and its roughly 1,500 residents. By the time it was over, eight of their number were dead, scores injured, and roughly 90% of the town completely obliterated. Not just ripped to pieces. Gone. Some survivors couldn't even locate the debris from their houses, it had been carried and scattered too great a distance. On Sunday, May 6, the NWS survey teams made the news official. This was the first EF5 tornado, the most violent windstorm on earth in just over eight years.

KAKE news
May 4 storm reports


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